cbitstruct is a C implementation of the bitstruct library. Credits to Erik Moqvist for the original bitstruct library available on Github and pip.
The goal is to provide the same API an idealy to be able to interchange import bitstruct and import cbitstruct as bitstruct.
Obvious increased performance comes with limitations described below.
pip3 install cbitstruct
Please refer to the bitstruct documentation as the aim of this library is to provide the same API with increased performance.
If you are not used to bitstruct, you should seriously consider using it first, before migrating to this library if you require higher performance.
Will it be lifted ?
All types except padding are limited to 64 bits
Maybe for 'raw' and 'text' types
May not work on big-endian architectures
Exceptions differ from bitstruct
Error messages are unclear
Will never be as clear as bitstruct
Python >= 3.5
Some limitations are there because I did not get the time or motivation to lift them up. Some other are deeply rooted into this library and may never be lifted.
Comparing to bitstruct
The script available in tests/test_perf.py measures performance comparing to the bitstruct library.
Here are the result "on my machine" (Ubuntu in Virtualbox on a laptop):
byteswap list of int | x 8.779 ( 8.638us -> 0.984us)
byteswap str | x 17.466 ( 9.158us -> 0.524us)
calcsize | x139.330 ( 61.060us -> 0.438us)
compiled pack | x 47.389 ( 35.968us -> 0.759us)
compiled pack_dict | x 27.184 ( 34.588us -> 1.272us)
compiled pack_into | x 32.037 ( 38.650us -> 1.206us)
compiled pack_into_dict | x 27.343 ( 37.718us -> 1.379us)
compiled unpack | x 33.928 ( 31.278us -> 0.922us)
compiled unpack_dict | x 21.627 ( 31.597us -> 1.461us)
compiled unpack_from | x 30.622 ( 29.977us -> 0.979us)
compiled unpack_from_dict | x 20.479 ( 30.936us -> 1.511us)
pack | x 77.003 ( 103.030us -> 1.338us)
pack_dict | x 53.254 ( 103.255us -> 1.939us)
pack_into | x 82.829 ( 119.373us -> 1.441us)
pack_into_dict | x 52.173 ( 108.135us -> 2.073us)
unpack | x 78.459 ( 91.896us -> 1.171us)
unpack_dict | x 40.287 ( 89.300us -> 2.217us)
unpack_from | x 77.027 ( 91.202us -> 1.184us)
unpack_from_dict | x 39.467 ( 88.043us -> 2.231us)
Disclaimer: these results may and will vary largely depending on the number of elements and types you pack/unpack. This script is provided as-is, and I will gladly accept an improved script providing more reliable results.
The dict API
The dict API is marginally slower than the traditional one. As the packing/unpacking performance is quite high, the overhead of performing dictionary lookups and hashing significantly increas pack and unpacking duration.